The correct option is A True
Modern periodic table is arranged in order of increasing atomic numbers and after filling of 7 elements in the second period after lithium the eighth element sodium has same property as that of the lithium and hence placed just below lithium. Same type of periodicity is seen in other periods also. Therefore according to the similarity in the properties they are arranged in the periodic table.
The periodic repetition of the elements with similar properties after certain regular interval when atoms are arranged in increasing order of atomic number is called periodicity. The periodic repetition of the properties is due to the recurrence of the similar valence shell configuration after certain regular interval.